Flashcards in Test 4 Deck (55):
what is metabolism?
all chemical reactions occurring in a cell
what is the body’s source of energy?
ATP, high energy bonds between phosphate groups release large amounts of energy when broken
what is a metabolic pathway?
a series of reactions that occur in a step by step fashion so each product is a substrate for another reaction
what is activation energy?
the amount of energy needed for a reaction to occur
what is a catalyst?
a substance that lowers Ea, speeding up the reaction
what is an enzyme?
a biological catalyst made out of protein
Describe the lock and key model.
1. substrates are attracted to the enzyme’s active site which is specific to the substrate shape
2. induced fit occurs, enzyme shape is altered to push the substrates together for a closer fit
3. cofactors and coenzymes chemically weaken substrates by adding or removing electrons
4. product is released and the enzyme is reused
what is a coenzyme?
organic component that binds to the enzyme’s active site
ex.) vitamins - B12, niacin, riboflavin
what is a cofactor?
an inorganic prosthetic group that works with the protein component to lower the Ea
ex.) Metal ions- iron, copper, zinc
what is a holoenzyme?
a functional enzyme
what is an apoenzyme?
the protein component of an enzyme
what are the 4 factors that affect enzyme activity?
1. adding more substrate
3. pH values
4. heavy metals
how does adding more substrate affect enzyme activity?
- increases the amount of collisions between substrate and enzyme
- when enzymes are functioning at it’s maximum capacity, if we increase substrates, the production level will not increase (limiting factor), flat line of graph is called saturation or plateau
- after reaching saturation/plateau, must add more enzymes to increase production levels
how does temperature affect enzyme activity?
- increases the collisions between substrate and enzyme
- if temperature shifts from the optimal temperature, the productivity decreases because the enzyme shape is altered
- can harm our bodies because when we get a fever, our body temperature increases above the optimal range and can denature our enzymes
how does pH affect enzyme activity?
- every enzyme has an optimal pH
ex.) pepsin in stomach has a pH of 2, trypsin in duodenum has a pH of 8
- a shift from the optimal range causes denaturation and decreases productivity to 0
how do heavy metals affect enzyme activity?
heavy metals (mercury and lead) have a greater affinity for electrons which affects the distribution of electrons in enzyme causing denaturation
what are the 2 forms of inhibition?
1. competitive inhibition
2. non-competitive or allosteric inhibition
what is competitive inhibition?
- when a chemical toxin prevents the substrates from binding to the active sites before the substrates do
ex.) carbon monoxide interferes with our hemoglobin, stopping oxygen from entering the body
what is non-competitive/allosteric inhibition?
- non-competitive inhibitor that binds to the allosteric site, altering the shape of the active site
how do we control productivity of enzymes?
- with the use of products acting as a non competitive inhibitors binding to the allosteric site, this can pause the production of products in order for the system to catch up
- once released, the enzyme function is restored
what is the hypothalamus?
- maintains homeostasis
- receives feedback from the body
- regulates pituitary in response
what is the pituitary gland?
master gland, secretes hormones that govern all other glands and their secretions
what is the thyroid stimulating hormone?
- secreted by the anterior pituitary gland
- stimulates cell growth and thyroxin hormone production and secretion from the thyroid gland
what is thyroxin?
a hormone that increases metabolism
describe the negative feedback loop.
- hypothalamus receives feedback from the body and sends information to the pituitary gland
- pituitary gland secretes TSH to the thyroid gland
- thyroid gland produces cell growth and thyroxin
- thyroxin increases metabolism
- low metabolism requires high TSH and vide versa
what element is required to produce thyroxin?
- lack of iodine leads to a lack of thyroxin, which means allow metabolism
- negative feedback loop sends information to the hypothalamus to secrete more TSH
- thyroxin still can not produce, further decreasing the level of metabolism
what is hypothyroidism?
- deficiency in thyroid hormone production due to a defect in thyroid gland
- low metabolism, always cold, lower iq
- can cause dwarfism or cretinism (low neural development)
what is hyperthyroidism?
- excess secretion of thyroid hormones
- always hot, hungry, sensitive to stimuli
- goiter develops, also known as graves’ disease
what is a goitrogen?
an agent that inhibits iodine intake, which results in a blockage of thyroid hormone synthesis
what is myxedema?
when water accumulates in the skin due to hypothyroidism, resulting in a think and puffy appearance
why is having smaller cells better for metabolism?
smaller cells have a smaller volume which means lower metabolic needs (oxygen, nutrients, waste removal) requiring less materials
surface area : volume ratio is bigger, meaning they are more efficient
what is diffusion?
the movement of molecules from high concentrations to low concentrations
what 3 factors affect the rate of diffusion?
what is osmosis? when does it occur?
the movement of H2O from low solute concentrations to high solute concentrations
occurs when there is unequal concentrated solutions separated by membrane, and when membrane is selective
what is a hypotonic solution?
- when solute concentration is greater inside than outside the membrane
- water enters cell by osmosis, animals cells burst immediately and plant cells undergo turgor pressure
what happens when a red blood cell is placed in a hypotonic solution?
bursts immediately, called lysis or hemolysis, due to the influx of water
what is a hypertonic solution?
when the solute concentration is greater outside than inside the membrane
water moves out of the cell and shrivels up, called cremated
what is an isotonic solution?
when the concentrations are equal on both sides of membrane, no net movement
what 3 things make up the membrane?
1. phospholipid bilayer
3. transmembrane protein
what does it mean to be hydrophilic?
has charges or is polar
what does it mean to be hydrophobic?
has no charger or is non-polar
what is the phospholipid bilayer
foundation of the cell membrane
what does cholesterol do for the membrane?
increases the viscosity of the cell membrane fluids giving the cell more structural support
what are the 5 types of transmembrane proteins?
1. channel protein
2. cell recognition
what is the phospholipid bilayer permeability?
semipermeable, permeable to non-polar molecules and water, non-permeable to polar molecules and macromolecules
what is the fluid mosaic model?
used to describe the structure of the membrane
what is a channel protein?
2 types, allows specific molecules to move through the plasma membrane
1. channel protein coupled to receptor protein
- triggered to open when receptor is triggered by a specific molecule
2. voltage gated channels
- triggered to open when a specific voltage is reached
what causes cystic fibrosis?
a faulty chloride channel protein, a thick mucus collects in the airways and in pancreatic and liver ducts
what is a receptor protein?
hormones, neurotransmitters, and other substances bind to the receptor protein to initiate cellular response
ex.) insulin receptor coupled to a channel protein
what is a cell recognition protein?
a specialized protein with a carbohydrate/glycoprotein that functions to identify the cell
what is a major histocompatibility complex?
a glycoprotein that is different for every person which is why organ transplants are difficult to achieve, foreign MHC glycoproteins are attacked by blood cells
what is a carrier protein?
1. facilitated diffusion
- selectively interacts with molecules and goes down the gradient, no ATP required
2. active transport
- selectively interacts with molecules and goes against the gradient, ATP required
what is an enzymatic protein?
enzymes that are bound to the membrane
what is does cholera bacteria do to the body?
releases a toxin that interferes with adenylate cyclase, involved in ATP metabolism
sodium and water leave intestinal cells and the individual may die from diarrhea